Such a condenser tumble-dryer has an at least approximately horizontally aligned and rotatably mounted clothes drum, two separate systems for the cooling air flow and the process air flow, a motor for driving the fan and clothes drum, an electric heating unit to heat up the process air, a condenser having a heat exchanger in which the process air is cooled and the moisture absorbed by the load to be dried is extracted by condensation, and facilities for removing the condensate.
Condenser tumble-dryers generally include a closed circuit for the process air ducting. During a drying process, the load to be dried is moved around in the rotatable drum and the heated process air is directed onto it, the air being blown in through apertures in the rear wall of the drum and flowing through the clothes drum in a roughly axial direction from the rear wall of the drum towards the front. The process air passes through a lint screen in the region around the loading aperture and reaches the condenser where the process air in the heat condenser is cooled by cooling air that has been sucked in from outside and condenses the moisture absorbed by the drying load. The condensate that has been collected in a collection container is removed using a pump. The process air that has been cooled and dehumidified in the heat exchanger is conveyed into the inside of the drum again via the heating element. The cooling air and process air are each conveyed by a fan, which is usually driven by the drive motor of the clothes drum.
In known tumble-dryers, mainly for reasons of space, a number of operationally necessary functional sub-assemblies and components, such as the drive motor, the fans for the cooling air and process air, the condenser, the condensate collection tray and pump and also facilities for conveying and ducting the process air and cooling air are integrated in a sub-assembly and installed underneath the clothes drum as a base module in the base area of the tumble-dryer.
Such a base module must be dimensioned in such a way that it can accommodate the components and must have sufficient mechanical stability in order to keep the installed components safe. The functional sub-assemblies and components have to be configured and assigned to each other such that their function can be used as effectively as possible in the operation of the tumble-dryer. The closed process air circuit system should be sealed off with minimum resistance in the air ducting so that energy losses and the escape of moisture can be avoided. In order to achieve this, in addition to corresponding air ducting in the base module, in particular the separation points from the end plate, which plate serves among other things to provide bearings at the front of the clothes drum and from the rear process air duct in which the heat register is generally disposed should be designed to be as air-tight as possible. Seal rings or seal cuffs are generally used for this purpose at the separation points of the sub-assemblies. The connections are, for example, mechanically secured with threaded joints such that they withstand the continuous stresses in long term operation.
In addition to the functional requirements, in the design of a base module aspects of rational manufacturing should be considered and where necessary balanced one against another. This affects in particular the manufacturing of the individual parts, which are made mainly of plastic by the injection molding process, but also the ease with which they can be fitted together during final assembly.
The prior art has disclosed various solutions for such base modules, depending on the purpose and on the focus of the design. In a base sub-assembly described in EP 0 434 169 A2, the functional parts are firmly mounted on a load-bearing unit that incorporates the base surface of the dryer. The housings for the fan wheels of the cooling air flow and process air flow are disposed symmetrically on both sides of the motor. The housings for the fan wheels each consist of two shells which are connected to each other by an integral hinge. The lower shells of the housings are mounted on to the load-bearing unit. After fitting the motor and putting in the fan wheels, the two collapsible upper parts are connected to the lower parts by a simple tilting movement and the fan housings are sealed in this way.
Even if the individual parts used for the air ducting are still easy to fit, maintaining a sufficient air-tightness of the air ducts is rather problematic in the construction method described. This applies in particular to the process air supply but also to the fan housings and the accommodation for the condenser.
The cited publication discloses air conduction facilities fixed onto the condenser at the sides to duct the process air and to separate the cooling air flow and process air flow. It is only with fairly considerable effort that it is possible to make said conduction facilities airtight such that the mixing of process air and cooling air and the escape of moisture into the room where the dryer is set up can be avoided.
DE 102 02 442 A1 discloses a push-in unit for a base module with allegedly improved air ducting. The apertures for the intake and outlet of cooling air are located in the area at the front of the tumble-dryer. The base module is pushed from the front into the frame of the housing as a prefabricated sub-assembly and secured in place. Integrated in the base module are spaces to accommodate the condenser, the cooling air fan and process air fan and air ducting and conduction ducts for the ducting of cooling air and process air. The front section of the process air duct is inserted from above, and the point of separation thereof is disposed in a roughly horizontal manner. The tumble-dryer is intended to achieve mechanical stability from the self-supporting housing which has a framework design. The combination of a metal frame and plastic base part is intensive in the use of materials, however, and presents problems during assembly because of the joining methods used.
A self-supporting base sub-assembly configured as part of the whole supporting structure is also known from DE 31 35 292 C2. This sub-assembly is made of plastic and is designed as a base part that fills the whole of the base area of the tumble-dryer, which base part forms the supporting structure together with an intermediate base and an upper part disposed one on top of the other. Molded into said base part are spaces to accommodate the functional parts and facilities for ducting the process air and cooling air. Said base part is part of the supporting structure of the device and in the base area it replaces the usual cross-struts and supporting rails. Corner posts are molded into the base part to provide connection to the housing, which is formed from a frame, said corner posts being joined to the perpendicular corner sections of the frame. This combination of a metal frame and plastic base part is very intensive in the use of materials and presents problems during assembly when connecting the load-bearing structure and the air ducts.
EP 1 508 636 A2 discloses an air suction device of a tumble-dryer, which device includes a housing that has on one side an air suction port to introduce external air; furthermore it has a fan that is built into the housing to generate the suction force; a drive motor to drive the fan, a guide duct to direct to a condensing device the air that has been sucked in; and a ventilation grille which is installed with a certain clearance from one side face of the housing, the suction port being disposed such that a duct can be formed between the ventilation grille and the lateral surface. The ventilation grille is equipped with a plurality of grille plates. The air suction device is at the same time used as a supporting stand for the part of the housing that is located above.
Furthermore, the aforementioned solutions share the common drawback that, in order to avoid energy losses and the escape of moisture, additional seals have to be inserted at the separation points of the components that have to be joined, in particular at the points of separation for the process air ducting.
Furthermore, the aforementioned solutions share the common drawback that, in order to avoid energy losses and the escape of moisture, additional seals have to be inserted at the separation points of the components that have to be joined, in particular at the points of separation for the process air ducting.